According to molecular orbital theory, the species among the following that does not exist is:

According to molecular orbital theory, the species among the following that does not exist is:

a. He2-
b. He2+
c. O22-
d. Be2

$$He_2^{-}$$ 0.5
$$He_2^+$$ 0.5
$$O^{2-}_2$$ 1
$$Be_2$$ 0